您可以使用AWS SDK来实现AWS S3通知，并检索到元数据信息。以下是一个使用Java AWS SDK的示例代码：

首先，您需要导入必要的库和配置您的AWS S3凭证：

import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.services.s3.event.S3EventNotification;
import com.amazonaws.services.s3.event.S3EventNotification.S3EventNotificationRecord;

public class S3NotificationExample {
    public static void main(String[] args) {
        // 配置AWS S3凭证
        String accessKey = "YOUR_ACCESS_KEY";
        String secretKey = "YOUR_SECRET_KEY";
        String region = "us-west-2";
        String bucketName = "YOUR_BUCKET_NAME";

        // 创建AWS S3客户端
        BasicAWSCredentials awsCredentials = new BasicAWSCredentials(accessKey, secretKey);
        AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
                .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(region, ""))
                .withCredentials(new AWSStaticCredentialsProvider(awsCredentials))
                .build();

        // 处理S3通知
        S3EventNotification notification = S3EventNotification.parseJson("YOUR_S3_NOTIFICATION_JSON");

        // 遍历通知记录
        for (S3EventNotificationRecord record : notification.getRecords()) {
            String objectKey = record.getS3().getObject().getKey();
            String metadata = s3Client.getObjectMetadata(bucketName, objectKey).toString();

            // 打印元数据信息
            System.out.println("Object Key: " + objectKey);
            System.out.println("Metadata: " + metadata);
        }
    }
}

请注意，您需要替换示例代码中的以下值：

• YOUR_ACCESS_KEY：您的AWS访问密钥
• YOUR_SECRET_KEY：您的AWS秘密密钥
• us-west-2：您的AWS S3存储桶所在的AWS区域
• YOUR_BUCKET_NAME：您的AWS S3存储桶名称
• YOUR_S3_NOTIFICATION_JSON：您收到的S3通知的JSON字符串

此代码将从AWS S3收到的通知中提取对象键，并使用getObjectMetadata方法检索对象的元数据。然后，它将打印对象键和元数据信息。